The invention concerns the formation of a terminal post for a storage battery.
Terminal posts of storage batteries, which are guided through the cover of the battery housing to the outside must be sealed in an electrolyte-tight manner against the cover, so that e.g., sulfuric acid, which is very active in a capillary sense, cannot leak to the outside in the case of lead batteries. Because of its capillary-active properties, sulfuric acid can penetrate through even the finest gaps and hair-line cracks.
Terminal posts are used for the execution of the electrical terminals of a battery through the battery cover, and these terminal posts are incorporated in the injection molding of the battery cover consisting of plastic. The electrical terminals are then later inserted into the terminal posts in the final assembly of the batteries. The following must be distinguished: 1) the sealing of the terminal posts against the battery cover, and 2) the sealing of the electrical terminals against the terminal posts. The instant invention concerns exclusively the domain of electrolyte-tight sealing between the terminal posts and the cover of storage batteries.
The use of rubber gaskets or sealing compounds based on a casting resin, fusion (melting) adhesive or the like is known for this purpose, but these are relatively expensive, and they may age or become loose due to mechanical defects during the period of use.
In practice, therefore, terminal posts have been used in recent years, which have in their foot region annular encircling ribs radially extending to the outside. These ribs form a so-called labyrinth seal in the cover during the manufacture of the cover from plastic.
However, even labyrinth seals of this type involve considerable problems, as has been described in detail in the recently published U.S. Pat. No. 5,077,892.
There is a problem in shaping the ribs on the outside in the foot region of the terminal posts. In lead batteries which are presently most commonly used, the terminal posts are cast from lead or cold compression molded from lead. In both cases, a two-part mold must be used, whose dividing plane lies in the plane of the axis of the terminal post, since, if it were positioned otherwise, the ribs which extend radially from the axis of the terminal post could not be removed from the mold.
This plane of division of the mold causes difficulties, since the terminal post removed from the mold still has a more or less intensely formed metal flash. If this flash is not carefully removed (which involves the corresponding costs), the ribs are not sufficiently tightly surrounded by the plastic mass in this region during the injection molding of the plastic cover, and thus hair-line gaps may be present in the labyrinth seal joining of the terminal post and the cover, by which means the electrolyte can leak from the battery.
A means for avoiding the undesired formation of flash on the labyrinth ribs is described in the already known U.S. Pat. No. 5,077,892. This means requires first of all, the manufacture of a homogeneous rod material from lead, which is then cut corresponding to the desired length of the terminal posts and then is processed in a lathe in order to produce the annular ribs free of flash and encircling in an annular manner the outside of the terminal posts. Of course, this is a very expensive means, in which a large mass production of terminal posts is not economical.
The task of the present invention is to seek a means for solving this problem by another cost-favorable means.
This task is resolved according to the invention, in that the foot region of the terminal post has a flange, which extends radially outward from the axis of the terminal post and that the ribs extending outwardly from the flange extend substantially parallel to the axis of the terminal post.
It is advantageous to provide the flange of the terminal post with ribs on its lower side as well as on its upper side.
Basic advantages are obtained by the new design of the labyrinth seal by means of the flange and the ribs extending therefrom.
First, it is an advantage that the new design of the labyrinth seal can be manufactured by mold (finished) casting or compression molding of the terminal posts, since this is a common process for large mass production and is the most cost-favorable.
A second advantage is produced by the fact that the new design of the labyrinth seal requires correspondingly other planes of division of the mold. The planes of division must now be arranged such that the radially extending flange with ribs extending parallel to the axis of the terminal post can be removed from the mold. Correspondingly, the plane of division is always selected such that the flange lies in its radial extent completely in the dividing plane, so that metal flash, which can form during casting or compression molding of the terminal post in the dividing plane can arise only on the outer diameter of the flange and in fact also only with radial extension to the outside.
It is appropriate to select the arrangement of the dividing plane such that it perpendicularly intersects the axis of the terminal post and is arranged at the level of the maximum outer diameter of the flange.
The flash extending radially outward on the outer edge or the maximum outer diameter of the flange is not a disadvantage with respect to the tightness of the labyrinth seal. The contrary is the case. It causes an increase in the theoretical length of the labyrinth path, through which an electrolyte must pass on its way from inside to outside. The effectiveness of the labyrinth seal is improved in this way. In the same way, it is acceptable in the terminal posts of the invention that metal flash is present on the outer periphery of the flange.
A third advantage results from the fact that the labyrinth seal of the new terminal post requires only a small height for incorporation in the battery cover (measured in the axial direction of the terminal post). In this way, the foot region of the terminal post does not extend very far into the inside space of the storage battery. The inside space of the storage battery can be better utilized by electrode plates which are incorporated at a higher level.